How are temporal variations in rainfall and hydrology accounted in SPARROW models?
|Back to Top| Actual water-quality load measurements show large year-to-year variations, driven largely by year-to-year variations in weather and flow conditions. For example, USGS long-term monitoring of water quality and streamflow show that the amount of nitrogen increased since the late 1960s; and that the amount was low during the drought in the late 1980s but high during the flood of 1993, even though the amount of nitrogen applied to fields in the basin was not significantly different (http://ks.water.usgs.gov/Kansas/pubs/fact-sheets/fs.135-00.html ). In addition, year-to-year variations in the mean-annual nitrogen load can range over as much as two orders of magnitude at monitoring stations, although the annual variations more typically range from 20-40 percent of the long-term mean annual load. Year-to-year variations, such as these, and within-year variations in contaminant concentration and streamflow are accounted for in a step prior to SPARROW spatial modeling (see questio
